IS THE SIGMA(2) RECEPTOR IN RAT-BRAIN RELATED TO THE K-III ANTIARRHYTHMIC DRUGS( CHANNEL OF CLASS)

The sigma2 receptor subtype was studied in rat cerebral cortex and in C6 glioma cells homogenates using various compounds including class II I antiarrhythmic drugs. The characteristics of )-[H-3]-3-(3-hydroxyphe nyl)-N-(1-propyl)piperidine ((+)-[H-3]-3-PPP) binding were assessed in competition experiments with different displacers which revealed the presence of sigma2 receptors. Various class III antiarrhythmic drugs i nhibited (+)-[H-3]-3-PPP binding with high affinity and their binding affinity was found to correlate with the potency of these compounds to increase the duration of action potentials measured in Purkinje fiber s in electrophysiological studies. Since class III antiarrhythmic drug s are known to interact with voltage-dependent K+ channels, the presen t results provide evidence that the (+)-[H-3]-3-PPP binding sites in r at brain possess the characteristics of K+ channels of class III antia rrhythmic drugs.